This document summarizes a study on the ecology and control of an introduced population of Southern Watersnakes in Machado Lake, California. Researchers captured over 300 watersnakes of all sizes using aquatic traps and hand captures, demonstrating an established population. Small snakes primarily ate introduced mosquitofish while larger snakes specialized on bullfrog larvae and sunfish. Capture rates declined over time during intensive trapping but varied between locations, making the overall population size hard to estimate. The population may spread watersnakes to other bodies of water containing native species.
This document summarizes a study on the metapopulation structure of Sacramento splittail, a semi-anadromous fish species in the San Francisco Estuary. The study found that there are two genetically distinct splittail populations that spawn in different tributaries but overlap in other areas. The populations are connected when climate patterns produce sufficient freshwater flows to connect their habitats. Using genetic and otolith microchemistry markers on fish sampled from different areas, the study aimed to understand connectivity between the populations and assess if they function as distinct evolutionarily significant units or as a metapopulation. The dynamic connectivity between the populations, controlled by variable climate, may be an important driver of gene flow.
The study examined the spatial and temporal distribution of native and alien fish larvae (ichthyoplankton) in three habitat types (marsh edge, shallow open water, and river channel) across one natural and three restored marshes in the Sacramento-San Joaquin Delta over two years. More than 25,000 fish larvae from 10 families were collected, with the assemblage dominated by alien fishes overall but with natives more abundant in winter/spring and aliens in summer. Abundance was highest in marsh edge habitats, suggesting it provides favorable rearing habitat. Restored sites varied in ichthyoplankton abundance depending on configuration, with the site having minimal tidal exchange and greater lower trophic productivity supporting
This document summarizes a study of chelonian species in the Delta do Jacuí State Park in Brazil. Four chelonian species were found, including the Orbigny's slider turtle which made up 66% of captures. Species occupied different habitat types, from permanent wetlands to temporary and human-influenced areas. The main threats were determined to be habitat destruction, fragmentation, and pollution from human activities.
This document summarizes a study that investigated how the size of the invasive snail Crepidula fornicata and algal particle density affect its feeding efficiency. C. fornicata was introduced from North America to Europe, where it threatens native species and aquaculture industries by competing for food and space. The study tested whether feeding efficiency, measured by particle removal rates, changes with snail size and algal concentration. It found that larger snails and higher algal densities resulted in higher particle removal rates. Understanding these relationships provides insights into C. fornicata's impacts on ecosystems and water quality where it has invaded.
The document summarizes a study on the abundance of commercial bivalves collected in Zone 6, Brgy. Bula, General Santos City, Philippines in 2009. The study aimed to determine the abundance index and identify species of bivalves present, measure physico-chemical water properties, and assess seagrass abundance. Gleaners collected bivalves daily which were monitored for 20 days. Water samples were taken during full and new moons to measure temperature, salinity, and total suspended solids. Seagrass cover was assessed using transects and quadrats. Statistical analysis using two-way ANOVA was conducted to determine differences in bivalve numbers collected over time and between species.
This paper examines fish species that have disappeared from catches around Bohol Island, Philippines over the period 1950-2007 based on interviews with local fishers. Generalized least squares tests showed steep declines to zero in catch for many species. Twenty of the 21 disappeared species were moderate to large bodied fish, including giant grouper and African pompano. Six were slow growing and four were late maturing. Species with large body size and high fishing pressure may be particularly vulnerable to overexploitation. Traditional ecological knowledge from fishers can provide long term catch data and inform conservation priorities when scientific data is limited.
Diversity and dispersion patterns of echinoderms in Babanlagan, Talisayan, Mi...Angelo Mark Walag
Echinoderms are fundamentally good indicators of health and status of coralline communities in marine waters. In this study, the diversity and distribution of echinoderm species were determined in Babanlagan, Talisayan, Misamis Oriental. In total, 387 individuals were collected coming from classes Echinoidea, Holothuroidea, Asteroidea, and Ophiuroidea. The majority of individuals collected were Protoreaster nodusus, which is a good indicator of reef health while the least abundant echinoderm species was Acanthaster planci. The pattern of distribution of majority of echinoderms was a clumped distribution while the other groups followed regular/uniform distribution, which may be due to limited dispersal ability and availability and available food sources. Moderate species diversity was also observed and species were rather similar in abundance, shown by the evenness index. This suggests good marine health, even under the threat of gleaning activities, active fishing, and habitat destruction. It is recommended that follow-up studies are conducted especially regarding monitoring of echinoderm species, to further assess the health of the intertidal zone in Babanlagan, Talisayan, Misamis Oriental.
The culture of maintenance ornamental fish among Iranian people is developing every day. One of the most important factors in selection aquarium fish is behavior of feeding. The feeding behavior of Guppy is poorly documented. In this experiment we study feeding behavior in P. reticulata by six treatments. Six aquariums with the same dimension were used and two points A & B with the maximum distance from each other were selected in each aquarium. In aquarium No.1 hand move with feeding in point A, in aquarium No.2 hand move without feeding in point A, in aquarium No.3 hand moves in point A and feeding in point B, in aquarium No.4 feeding without hand move in point B, in aquarium No.5 in semi dark conditions hand move with feeding in point A and finally in aquarium No.6 in darkness conditions hand move with feeding in point A were done. In aquarium No.1, 94% of fish moved to point A and in aquarium No.2 it was about 92%. In aquarium No.3, 95.5% of fish moved to point A and in Aquarium No.4, 74.5% of fish moved to point B. In aquarium No 5 and 6, 96% and 99.5% of fish moved and didn’t move to point A, respectively. Our results showed that this species is a visual feeder and a good aquarium fish for their feeding behavior.
Article Citation:
Rajaei M, Nematollahi MA, Bahmaninezhad A and Lotfizadeh A.
Behavior of Feeding in Guppy: Poecilia reticulata.
Journal of Research in Animal Sciences (2012) 1(1): 001-006.
Full Text:
http://janimalsciences.com/documents/AS0004.pdf
This document summarizes a study on the metapopulation structure of Sacramento splittail, a semi-anadromous fish species in the San Francisco Estuary. The study found that there are two genetically distinct splittail populations that spawn in different tributaries but overlap in other areas. The populations are connected when climate patterns produce sufficient freshwater flows to connect their habitats. Using genetic and otolith microchemistry markers on fish sampled from different areas, the study aimed to understand connectivity between the populations and assess if they function as distinct evolutionarily significant units or as a metapopulation. The dynamic connectivity between the populations, controlled by variable climate, may be an important driver of gene flow.
The study examined the spatial and temporal distribution of native and alien fish larvae (ichthyoplankton) in three habitat types (marsh edge, shallow open water, and river channel) across one natural and three restored marshes in the Sacramento-San Joaquin Delta over two years. More than 25,000 fish larvae from 10 families were collected, with the assemblage dominated by alien fishes overall but with natives more abundant in winter/spring and aliens in summer. Abundance was highest in marsh edge habitats, suggesting it provides favorable rearing habitat. Restored sites varied in ichthyoplankton abundance depending on configuration, with the site having minimal tidal exchange and greater lower trophic productivity supporting
This document summarizes a study of chelonian species in the Delta do Jacuí State Park in Brazil. Four chelonian species were found, including the Orbigny's slider turtle which made up 66% of captures. Species occupied different habitat types, from permanent wetlands to temporary and human-influenced areas. The main threats were determined to be habitat destruction, fragmentation, and pollution from human activities.
This document summarizes a study that investigated how the size of the invasive snail Crepidula fornicata and algal particle density affect its feeding efficiency. C. fornicata was introduced from North America to Europe, where it threatens native species and aquaculture industries by competing for food and space. The study tested whether feeding efficiency, measured by particle removal rates, changes with snail size and algal concentration. It found that larger snails and higher algal densities resulted in higher particle removal rates. Understanding these relationships provides insights into C. fornicata's impacts on ecosystems and water quality where it has invaded.
The document summarizes a study on the abundance of commercial bivalves collected in Zone 6, Brgy. Bula, General Santos City, Philippines in 2009. The study aimed to determine the abundance index and identify species of bivalves present, measure physico-chemical water properties, and assess seagrass abundance. Gleaners collected bivalves daily which were monitored for 20 days. Water samples were taken during full and new moons to measure temperature, salinity, and total suspended solids. Seagrass cover was assessed using transects and quadrats. Statistical analysis using two-way ANOVA was conducted to determine differences in bivalve numbers collected over time and between species.
This paper examines fish species that have disappeared from catches around Bohol Island, Philippines over the period 1950-2007 based on interviews with local fishers. Generalized least squares tests showed steep declines to zero in catch for many species. Twenty of the 21 disappeared species were moderate to large bodied fish, including giant grouper and African pompano. Six were slow growing and four were late maturing. Species with large body size and high fishing pressure may be particularly vulnerable to overexploitation. Traditional ecological knowledge from fishers can provide long term catch data and inform conservation priorities when scientific data is limited.
Diversity and dispersion patterns of echinoderms in Babanlagan, Talisayan, Mi...Angelo Mark Walag
Echinoderms are fundamentally good indicators of health and status of coralline communities in marine waters. In this study, the diversity and distribution of echinoderm species were determined in Babanlagan, Talisayan, Misamis Oriental. In total, 387 individuals were collected coming from classes Echinoidea, Holothuroidea, Asteroidea, and Ophiuroidea. The majority of individuals collected were Protoreaster nodusus, which is a good indicator of reef health while the least abundant echinoderm species was Acanthaster planci. The pattern of distribution of majority of echinoderms was a clumped distribution while the other groups followed regular/uniform distribution, which may be due to limited dispersal ability and availability and available food sources. Moderate species diversity was also observed and species were rather similar in abundance, shown by the evenness index. This suggests good marine health, even under the threat of gleaning activities, active fishing, and habitat destruction. It is recommended that follow-up studies are conducted especially regarding monitoring of echinoderm species, to further assess the health of the intertidal zone in Babanlagan, Talisayan, Misamis Oriental.
The culture of maintenance ornamental fish among Iranian people is developing every day. One of the most important factors in selection aquarium fish is behavior of feeding. The feeding behavior of Guppy is poorly documented. In this experiment we study feeding behavior in P. reticulata by six treatments. Six aquariums with the same dimension were used and two points A & B with the maximum distance from each other were selected in each aquarium. In aquarium No.1 hand move with feeding in point A, in aquarium No.2 hand move without feeding in point A, in aquarium No.3 hand moves in point A and feeding in point B, in aquarium No.4 feeding without hand move in point B, in aquarium No.5 in semi dark conditions hand move with feeding in point A and finally in aquarium No.6 in darkness conditions hand move with feeding in point A were done. In aquarium No.1, 94% of fish moved to point A and in aquarium No.2 it was about 92%. In aquarium No.3, 95.5% of fish moved to point A and in Aquarium No.4, 74.5% of fish moved to point B. In aquarium No 5 and 6, 96% and 99.5% of fish moved and didn’t move to point A, respectively. Our results showed that this species is a visual feeder and a good aquarium fish for their feeding behavior.
Article Citation:
Rajaei M, Nematollahi MA, Bahmaninezhad A and Lotfizadeh A.
Behavior of Feeding in Guppy: Poecilia reticulata.
Journal of Research in Animal Sciences (2012) 1(1): 001-006.
Full Text:
http://janimalsciences.com/documents/AS0004.pdf
This study examined the effects of 4-inch suction dredge mining on benthic macroinvertebrates in 3rd to 4th order streams in southwestern Oregon. The author evaluated four mining claim operations across three creeks by comparing treatment reaches that were dredged to undredged control reaches. Results showed no significant differences in macroinvertebrate density or diversity between treatment and control areas. However, taxa richness was significantly higher one month after dredging. Collector-filterers were significantly lower in dredged areas one month later as well. The study had constraints like small sample sizes that make results tentative. Differences among sites also confounded the results.
Sharks are top predators, but little was known about bonnethead sharks' feeding ecology in Tampa Bay. The author studied the diets of 13 bonnethead sharks captured in Tampa Bay. The study found the main dietary components were blue crab, common spider crab, and seagrass, with seagrass having the highest index of relative importance. While seagrass made up most of the diets numerically, it is unclear if bonnetheads actively forage seagrass. More research with larger sample sizes is needed to better understand bonnethead feeding ecology in Tampa Bay and determine if environmental changes have impacted their diets.
This document summarizes Laurent J. Lamarque's PhD oral examination on the ecology and evolution of invasive maple tree species. The examination focused on (1) population demography, (2) traits promoting invasiveness, and (3) genetic and environmental determinism of traits in invasive maple trees. Key findings included that invasive populations of Acer negundo had higher abundance and increased plasticity compared to native populations, but this was not true for Acer platanoides. Reciprocal common gardens showed evidence of genetic differentiation and pre-adapted plasticity in Acer negundo, but more research is needed to understand genetic-environment interactions. The conclusion was that tree invaders are not fundamentally different from other invaders
This document summarizes restrictions on sharing and distributing an article from a journal published by Elsevier. The attached copy of the article is for the author's internal non-commercial use, including for instruction and sharing with colleagues. Other uses like reproduction, distribution, selling copies, or posting to websites are prohibited without permission. Authors are generally allowed to post their version of the article to their personal or institutional websites or repositories. The document provides a link for authors to get more information on Elsevier's archiving and manuscript policies.
This study examines the role of predation in regulating the spread of the invasive barnacle Balanus glandula along the South African coast. The authors monitored the abundance and range of B. glandula annually from 2012-2014 and found it continued expanding. Field observations and feeding experiments with native whelks revealed they generally consumed more of the native barnacle Notomegabalanus algicola than the invasive B. glandula. However, this predation-driven biotic resistance was not sufficient to contain the expansion of B. glandula. Structural defenses of B. glandula, like thicker shells, may explain the avoidance by whelks.
This document summarizes a study that examines the effects of invasive riparian plant species on macroinvertebrate populations in cold water streams. The researchers hypothesize that reaches with invasive species will have higher pollution tolerance scores and lower macroinvertebrate diversity than restored reaches. Samples will be taken from one degraded reach dominated by invasive buckthorn and garlic mustard, and one restored reach. Macroinvertebrates will be identified and riparian plant biomass will be estimated to determine impacts on aquatic communities.
Analyses of Community Attributes of Meiofauna Under A Pollution Regime in the...Agriculture Journal IJOEAR
— Meiofauna community attributes of the lower Bonny estuary was investigated under a pollution regime. This is germane because of the strategic importance of meiofauna in the food chain and the sustenance of any aquatic ecosystem. Five stations representing diverse land based activities such as refuse dump site, fuel depot, fishing-landing areas, residential housing and a station located upstream (control) were chosen for investigation. The meiofauna samples were collected from sediments in three replicate spots per station per sampling months at low tide. Sediment samples were stirred through (63-212nm) meshes to separate meiofauna and organic debris. Meiofauna samples were processed by first washing Meiofauna through a sieve of fine mesh size made of silk material, in order to wash off formation and excess silt or mud. Meiofauna samples were sorted out and identified using standard keys. Result from field studies indicate that meiofauna population abundance and diversity varied slightly between stations and seasons. There was however, no established trend. Meiofauna were generally more abundant in the rainy season than in the dry season. In general, pollution indicator meiofaunal taxa were more in all stations except the control station; the increasing impact of pollutants in the river led to a rise in the relative abundance of r-strategist genera like Chromadora. We conclude that the application of meiofaunal indices can be a useful tool for assessing the environmental quality of estuarine ecosystems.
Reptile Diversity in Mt. Matutum Protected Landscape, South Cotabato, Philipp...Innspub Net
Reptiles are highly diversewith high percentage of endemism in the Philippines. However, reptile diversity in Mindanao, the second largest island in the country,is poorly known. To determine the species richness, diversity, endemism and conservation status of reptiles, this study was conducted from August to December 2013in six sampling sites of Mt. Matutum Protected Landscape (MMPL), South Cotabato.Cruising methodwasdone in the six sampling sites of MMPL. Paleontological Statistics Software Package (PAST) version 3.06 was used to determine the biodiversity indices, similarity index, and Kruskal-Wallis test. Thirteen species of reptiles belonging to five families and 11 genera with percentage endemism of46.15% were documented. High species diversity of reptiles with more or less even distribution was recorded in MMPL. Among the sampled sites, sampling site 1, a disturbed lowland dipterocarp forest had the highest species diversityand endemism.Sphenomorphusvariegatus was the most abundant species. Tropidophoruspartelloi, the only Mindanao Island endemic species was only found in the disturbed and undisturbed montane forests. Most of the documented species were under the Least Concern status. Bray-Curtis cluster analysis showed that sites 2 and 5 had the highest similarity percentage (68%) while Kruskal-Wallis test showed no significant difference between samples in disturbedand undisturbed sites. Threats to the reptiles of MMPL were observed to be the conversion of forest to farmland and hunting thus implying the need for protection of habitats and conservation of species in MMPL.
Bachelor's thesis _ Current and historical distribution of the endemic Santa ...DeannaRhoades
I investigated the current and past range of the endemic Santa Cruz kangaroo rat, Dipodomys venustus venustus, by surveying (via Sherman live trapping) localities with suitable habitat based on historical range records and GIS habitat mapping. Live-trapping captured no kangaroo rats at any of the sites chosen for suitability. Potential explanations and recommended conservation actions are discussed. Thesis advisor: Gage H. Dayton.
Received a $1000 grant from the Ken Norris Natural History Center to conduct research.
Species Diversity of Polychaete Worms from Some Selected Freshwater Environme...ijtsrd
The number of freshwater species in the world is quite small when compared with the vast number of marine species. There are several marine forms which are penetrated brackish and freshwater but remain unable to breed there while others have adapted sufficiently to remain for their entire life span. Polychaetes are commonly found in Indian estuaries, among 152 species recorded, 119 species from the east coast, 10 species from both east and west coasts. A total of 8 species were identified along Thenkasi District. Macro benthic polychaetes highlighted the presence of indicator species at all stations. Most of the benthic studies explored that Nereididae is the dominant species. The polychaetes observed throughout this study were a similar size and this is a clear indication of extreme disturbance imposed on the sediment. The present findings show macrobenthic polychaete diversity rich all along the Thenkasi District of Tamil Nadu. S. Balasubramanian | T. Citarasu | S. Lazarus | A. Renu "Species Diversity of Polychaete Worms from Some Selected Freshwater Environment of Thenkasi District, Tamil Nadu" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26516.pdfPaper URL: https://www.ijtsrd.com/biological-science/zoology/26516/species-diversity-of-polychaete-worms-from-some-selected-freshwater-environment-of-thenkasi-district-tamil-nadu/s-balasubramanian
This document discusses the ecology and evolution of interactions between seaweeds and their herbivores on coral reefs. It finds that herbivory, primarily from fishes and sea urchins, is the dominant force controlling the distribution and abundance of seaweeds. Seaweeds have evolved various defensive traits, such as chemical deterrents, to escape or reduce herbivory. These defenses also indirectly affect smaller grazers that live on the seaweeds and receive protection from predators. The strong herbivore pressure on coral reefs has selected for more potent chemical defenses in tropical seaweeds compared to temperate ones.
The document summarizes a study of crustacean communities in Anchar Lake, Kashmir. Eleven crustacean species from five families were identified. Population levels fluctuated seasonally, with maximum levels in summer and minimum in winter. Daphnidae was the most abundant family. The population dynamics were influenced by water level fluctuations and macrophyte density. The crustacean community composition reflected the shallow, eutrophic nature of the lake.
morris and glasgow 2001 wb 113-202-210 AMREJamin Glasgow
American Redstarts were studied during spring and fall migration on Appledore Island, Maine from 1990 to 1999. Several key differences were observed between seasons:
- In spring, males arrived earlier than females and adults arrived earlier than young birds. In fall, arrival times did not differ between males and females or adults and young.
- Recaptures of banded birds occurring at least one day after initial capture were more common in fall than spring.
- While minimum stopover lengths did not differ between seasons, recaptured birds increased in mass more significantly during fall stopovers compared to spring.
- Rates of mass increase estimated by regression, however, were greater during spring stopovers than fall.
This document provides a literature review on guppies (Poecilia reticulata) and Lake Sebu, Philippines. It discusses the taxonomy, morphology, behavior, habitat, and feeding of guppies. It also describes the location, climate, population, industries, and festivals of Lake Sebu. Finally, it reviews the SHAPE software which is used to analyze biological shapes through elliptic Fourier descriptors and principal component analysis.
Z & edwards (2011) extinction of a shark population in the archipelago of sai...Projeto Golfinho Rotador
This document discusses the extinction of reef sharks (Carcharhinus spp.) from the remote Archipelago of Saint Paul's Rocks in the equatorial Atlantic. The authors review historical records from visits to the archipelago dating back to the mid-20th century, which consistently noted the presence of many sharks. However, more recent expeditions in the last decade have found no reef sharks despite extensive underwater surveys. All analyses conclude that one species, Carcharhinus galapagensis, is now locally extinct at the archipelago following a sharp decline after the start of commercial fishing in the 1950s. The related species Carcharhinus falciformis may still occasionally visit but no longer has a resident population due to
This document summarizes a study on the rockfish resources of the south central California coast. Researchers from California Polytechnic State University placed observers on party boats from 2003-2005 to record catch data by species, including catch per unit effort and mean size. They supplemented this with historical catch data from 1980-1998 from the California Department of Fish and Game and Pacific Gas & Electric. The study aims to analyze population trends over the past 25 years for various rockfish species in the region and compare sizes over time. Preliminary results found fluctuating catch rates but no consistent declining trends, except for bocaccio rockfish. Mean sizes were generally above maturity levels.
species composition of intertidal marine macroalgae in san francisco canaoay,...INFOGAIN PUBLICATION
The Philippines occupy the north of coral triangle, a huge area overlapping the Indian Ocean and the Pacific Ocean, and is famous for its extremely rich marine biodiversity. The taxonomical study of seaweeds started on the year 1750 and towards the end of the 20th century[1]. In Ilocos Sur, a comprehensive study on the marine benthic algae was made by Domingo in 1988.In this study, he reported 103 species, with 91 species reported for the first time for the province[2].As to this date, no taxonomical study made in San Francisco-Canaoay. This study used site description, Exhaustive Line Transect Method.The macroalgae recorded in San Francisco-Canaoay in the open area of the coastlines includeone genus&sevenspecies of Phaeophyta, one genus&one species of Chlorophyta, and one genus &nine species of Rhodophyta. The larger number of Rhodophyta can be attributed to the presence of abundant nutrients in the area and the luminosity of light of 35, 000 Lux value, which was favorable for the photosynthetic macroalgae.The specimens identified,58% were Phaeophyta, 34% were Chlorophyta, and 8% were Rhodophyta.There were more red algaes (Rhodophyta) in the open area due to the nature of these plant-like protists to thrive in running water with many nutrients. The number of brown algaes (phaeophyta) are not affected by the conditions of the water because of their toughness as compared to the aforementioned nature of red algaes[3].
The Riverhead Foundation is a marine conservation organization that performs necropsies on sea turtles and marine mammals to further their understanding of threats to these species and educate the public. The document describes the objectives and findings of an internship where the author observed necropsies on 36 sea turtles and recorded data on cause of death and biological characteristics. Major threats identified were boat strikes and plastic ingestion. The necropsy data collected will help the Foundation in their conservation efforts of at-risk sea turtle species in the New York area.
Bachelor's thesis poster (Deanna K. Rhoades)DeannaRhoades
Bachelor's thesis, Undergraduate Symposium poster: "Current and historical distribution of the endemic Santa Cruz
kangaroo rat, Dipodomys venustus venustus"
"Evaluaciones del desempeño ambiental - Perú 2016", es un estudio preparado por la Organización para la Cooperación y el Desarrollo Económicos – OCDE y la Comisión Económica para América Latina y el Caribe – CEPAL.
https://www.oecd.org/environment/country-reviews/16-00313%20Evaluacion%20desempeno-Peru-WEB.pdf
Reforma de la gobernanza pública en Perú - Aspectos claves 2016Paulo Pantigoso
"Reforma de la gobernanza pública en Perú - Aspectos claves 2016", es un estudio preparado por la Organización para la Cooperación y el Desarrollo Económicos – OCDE.
https://www.oecd.org/gov/public-governance-review-peru-highlights-es.pdf
This study examined the effects of 4-inch suction dredge mining on benthic macroinvertebrates in 3rd to 4th order streams in southwestern Oregon. The author evaluated four mining claim operations across three creeks by comparing treatment reaches that were dredged to undredged control reaches. Results showed no significant differences in macroinvertebrate density or diversity between treatment and control areas. However, taxa richness was significantly higher one month after dredging. Collector-filterers were significantly lower in dredged areas one month later as well. The study had constraints like small sample sizes that make results tentative. Differences among sites also confounded the results.
Sharks are top predators, but little was known about bonnethead sharks' feeding ecology in Tampa Bay. The author studied the diets of 13 bonnethead sharks captured in Tampa Bay. The study found the main dietary components were blue crab, common spider crab, and seagrass, with seagrass having the highest index of relative importance. While seagrass made up most of the diets numerically, it is unclear if bonnetheads actively forage seagrass. More research with larger sample sizes is needed to better understand bonnethead feeding ecology in Tampa Bay and determine if environmental changes have impacted their diets.
This document summarizes Laurent J. Lamarque's PhD oral examination on the ecology and evolution of invasive maple tree species. The examination focused on (1) population demography, (2) traits promoting invasiveness, and (3) genetic and environmental determinism of traits in invasive maple trees. Key findings included that invasive populations of Acer negundo had higher abundance and increased plasticity compared to native populations, but this was not true for Acer platanoides. Reciprocal common gardens showed evidence of genetic differentiation and pre-adapted plasticity in Acer negundo, but more research is needed to understand genetic-environment interactions. The conclusion was that tree invaders are not fundamentally different from other invaders
This document summarizes restrictions on sharing and distributing an article from a journal published by Elsevier. The attached copy of the article is for the author's internal non-commercial use, including for instruction and sharing with colleagues. Other uses like reproduction, distribution, selling copies, or posting to websites are prohibited without permission. Authors are generally allowed to post their version of the article to their personal or institutional websites or repositories. The document provides a link for authors to get more information on Elsevier's archiving and manuscript policies.
This study examines the role of predation in regulating the spread of the invasive barnacle Balanus glandula along the South African coast. The authors monitored the abundance and range of B. glandula annually from 2012-2014 and found it continued expanding. Field observations and feeding experiments with native whelks revealed they generally consumed more of the native barnacle Notomegabalanus algicola than the invasive B. glandula. However, this predation-driven biotic resistance was not sufficient to contain the expansion of B. glandula. Structural defenses of B. glandula, like thicker shells, may explain the avoidance by whelks.
This document summarizes a study that examines the effects of invasive riparian plant species on macroinvertebrate populations in cold water streams. The researchers hypothesize that reaches with invasive species will have higher pollution tolerance scores and lower macroinvertebrate diversity than restored reaches. Samples will be taken from one degraded reach dominated by invasive buckthorn and garlic mustard, and one restored reach. Macroinvertebrates will be identified and riparian plant biomass will be estimated to determine impacts on aquatic communities.
Analyses of Community Attributes of Meiofauna Under A Pollution Regime in the...Agriculture Journal IJOEAR
— Meiofauna community attributes of the lower Bonny estuary was investigated under a pollution regime. This is germane because of the strategic importance of meiofauna in the food chain and the sustenance of any aquatic ecosystem. Five stations representing diverse land based activities such as refuse dump site, fuel depot, fishing-landing areas, residential housing and a station located upstream (control) were chosen for investigation. The meiofauna samples were collected from sediments in three replicate spots per station per sampling months at low tide. Sediment samples were stirred through (63-212nm) meshes to separate meiofauna and organic debris. Meiofauna samples were processed by first washing Meiofauna through a sieve of fine mesh size made of silk material, in order to wash off formation and excess silt or mud. Meiofauna samples were sorted out and identified using standard keys. Result from field studies indicate that meiofauna population abundance and diversity varied slightly between stations and seasons. There was however, no established trend. Meiofauna were generally more abundant in the rainy season than in the dry season. In general, pollution indicator meiofaunal taxa were more in all stations except the control station; the increasing impact of pollutants in the river led to a rise in the relative abundance of r-strategist genera like Chromadora. We conclude that the application of meiofaunal indices can be a useful tool for assessing the environmental quality of estuarine ecosystems.
Reptile Diversity in Mt. Matutum Protected Landscape, South Cotabato, Philipp...Innspub Net
Reptiles are highly diversewith high percentage of endemism in the Philippines. However, reptile diversity in Mindanao, the second largest island in the country,is poorly known. To determine the species richness, diversity, endemism and conservation status of reptiles, this study was conducted from August to December 2013in six sampling sites of Mt. Matutum Protected Landscape (MMPL), South Cotabato.Cruising methodwasdone in the six sampling sites of MMPL. Paleontological Statistics Software Package (PAST) version 3.06 was used to determine the biodiversity indices, similarity index, and Kruskal-Wallis test. Thirteen species of reptiles belonging to five families and 11 genera with percentage endemism of46.15% were documented. High species diversity of reptiles with more or less even distribution was recorded in MMPL. Among the sampled sites, sampling site 1, a disturbed lowland dipterocarp forest had the highest species diversityand endemism.Sphenomorphusvariegatus was the most abundant species. Tropidophoruspartelloi, the only Mindanao Island endemic species was only found in the disturbed and undisturbed montane forests. Most of the documented species were under the Least Concern status. Bray-Curtis cluster analysis showed that sites 2 and 5 had the highest similarity percentage (68%) while Kruskal-Wallis test showed no significant difference between samples in disturbedand undisturbed sites. Threats to the reptiles of MMPL were observed to be the conversion of forest to farmland and hunting thus implying the need for protection of habitats and conservation of species in MMPL.
Bachelor's thesis _ Current and historical distribution of the endemic Santa ...DeannaRhoades
I investigated the current and past range of the endemic Santa Cruz kangaroo rat, Dipodomys venustus venustus, by surveying (via Sherman live trapping) localities with suitable habitat based on historical range records and GIS habitat mapping. Live-trapping captured no kangaroo rats at any of the sites chosen for suitability. Potential explanations and recommended conservation actions are discussed. Thesis advisor: Gage H. Dayton.
Received a $1000 grant from the Ken Norris Natural History Center to conduct research.
Species Diversity of Polychaete Worms from Some Selected Freshwater Environme...ijtsrd
The number of freshwater species in the world is quite small when compared with the vast number of marine species. There are several marine forms which are penetrated brackish and freshwater but remain unable to breed there while others have adapted sufficiently to remain for their entire life span. Polychaetes are commonly found in Indian estuaries, among 152 species recorded, 119 species from the east coast, 10 species from both east and west coasts. A total of 8 species were identified along Thenkasi District. Macro benthic polychaetes highlighted the presence of indicator species at all stations. Most of the benthic studies explored that Nereididae is the dominant species. The polychaetes observed throughout this study were a similar size and this is a clear indication of extreme disturbance imposed on the sediment. The present findings show macrobenthic polychaete diversity rich all along the Thenkasi District of Tamil Nadu. S. Balasubramanian | T. Citarasu | S. Lazarus | A. Renu "Species Diversity of Polychaete Worms from Some Selected Freshwater Environment of Thenkasi District, Tamil Nadu" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26516.pdfPaper URL: https://www.ijtsrd.com/biological-science/zoology/26516/species-diversity-of-polychaete-worms-from-some-selected-freshwater-environment-of-thenkasi-district-tamil-nadu/s-balasubramanian
This document discusses the ecology and evolution of interactions between seaweeds and their herbivores on coral reefs. It finds that herbivory, primarily from fishes and sea urchins, is the dominant force controlling the distribution and abundance of seaweeds. Seaweeds have evolved various defensive traits, such as chemical deterrents, to escape or reduce herbivory. These defenses also indirectly affect smaller grazers that live on the seaweeds and receive protection from predators. The strong herbivore pressure on coral reefs has selected for more potent chemical defenses in tropical seaweeds compared to temperate ones.
The document summarizes a study of crustacean communities in Anchar Lake, Kashmir. Eleven crustacean species from five families were identified. Population levels fluctuated seasonally, with maximum levels in summer and minimum in winter. Daphnidae was the most abundant family. The population dynamics were influenced by water level fluctuations and macrophyte density. The crustacean community composition reflected the shallow, eutrophic nature of the lake.
morris and glasgow 2001 wb 113-202-210 AMREJamin Glasgow
American Redstarts were studied during spring and fall migration on Appledore Island, Maine from 1990 to 1999. Several key differences were observed between seasons:
- In spring, males arrived earlier than females and adults arrived earlier than young birds. In fall, arrival times did not differ between males and females or adults and young.
- Recaptures of banded birds occurring at least one day after initial capture were more common in fall than spring.
- While minimum stopover lengths did not differ between seasons, recaptured birds increased in mass more significantly during fall stopovers compared to spring.
- Rates of mass increase estimated by regression, however, were greater during spring stopovers than fall.
This document provides a literature review on guppies (Poecilia reticulata) and Lake Sebu, Philippines. It discusses the taxonomy, morphology, behavior, habitat, and feeding of guppies. It also describes the location, climate, population, industries, and festivals of Lake Sebu. Finally, it reviews the SHAPE software which is used to analyze biological shapes through elliptic Fourier descriptors and principal component analysis.
Z & edwards (2011) extinction of a shark population in the archipelago of sai...Projeto Golfinho Rotador
This document discusses the extinction of reef sharks (Carcharhinus spp.) from the remote Archipelago of Saint Paul's Rocks in the equatorial Atlantic. The authors review historical records from visits to the archipelago dating back to the mid-20th century, which consistently noted the presence of many sharks. However, more recent expeditions in the last decade have found no reef sharks despite extensive underwater surveys. All analyses conclude that one species, Carcharhinus galapagensis, is now locally extinct at the archipelago following a sharp decline after the start of commercial fishing in the 1950s. The related species Carcharhinus falciformis may still occasionally visit but no longer has a resident population due to
This document summarizes a study on the rockfish resources of the south central California coast. Researchers from California Polytechnic State University placed observers on party boats from 2003-2005 to record catch data by species, including catch per unit effort and mean size. They supplemented this with historical catch data from 1980-1998 from the California Department of Fish and Game and Pacific Gas & Electric. The study aims to analyze population trends over the past 25 years for various rockfish species in the region and compare sizes over time. Preliminary results found fluctuating catch rates but no consistent declining trends, except for bocaccio rockfish. Mean sizes were generally above maturity levels.
species composition of intertidal marine macroalgae in san francisco canaoay,...INFOGAIN PUBLICATION
The Philippines occupy the north of coral triangle, a huge area overlapping the Indian Ocean and the Pacific Ocean, and is famous for its extremely rich marine biodiversity. The taxonomical study of seaweeds started on the year 1750 and towards the end of the 20th century[1]. In Ilocos Sur, a comprehensive study on the marine benthic algae was made by Domingo in 1988.In this study, he reported 103 species, with 91 species reported for the first time for the province[2].As to this date, no taxonomical study made in San Francisco-Canaoay. This study used site description, Exhaustive Line Transect Method.The macroalgae recorded in San Francisco-Canaoay in the open area of the coastlines includeone genus&sevenspecies of Phaeophyta, one genus&one species of Chlorophyta, and one genus &nine species of Rhodophyta. The larger number of Rhodophyta can be attributed to the presence of abundant nutrients in the area and the luminosity of light of 35, 000 Lux value, which was favorable for the photosynthetic macroalgae.The specimens identified,58% were Phaeophyta, 34% were Chlorophyta, and 8% were Rhodophyta.There were more red algaes (Rhodophyta) in the open area due to the nature of these plant-like protists to thrive in running water with many nutrients. The number of brown algaes (phaeophyta) are not affected by the conditions of the water because of their toughness as compared to the aforementioned nature of red algaes[3].
The Riverhead Foundation is a marine conservation organization that performs necropsies on sea turtles and marine mammals to further their understanding of threats to these species and educate the public. The document describes the objectives and findings of an internship where the author observed necropsies on 36 sea turtles and recorded data on cause of death and biological characteristics. Major threats identified were boat strikes and plastic ingestion. The necropsy data collected will help the Foundation in their conservation efforts of at-risk sea turtle species in the New York area.
Bachelor's thesis poster (Deanna K. Rhoades)DeannaRhoades
Bachelor's thesis, Undergraduate Symposium poster: "Current and historical distribution of the endemic Santa Cruz
kangaroo rat, Dipodomys venustus venustus"
"Evaluaciones del desempeño ambiental - Perú 2016", es un estudio preparado por la Organización para la Cooperación y el Desarrollo Económicos – OCDE y la Comisión Económica para América Latina y el Caribe – CEPAL.
https://www.oecd.org/environment/country-reviews/16-00313%20Evaluacion%20desempeno-Peru-WEB.pdf
Reforma de la gobernanza pública en Perú - Aspectos claves 2016Paulo Pantigoso
"Reforma de la gobernanza pública en Perú - Aspectos claves 2016", es un estudio preparado por la Organización para la Cooperación y el Desarrollo Económicos – OCDE.
https://www.oecd.org/gov/public-governance-review-peru-highlights-es.pdf
The document surveys two ponds near an apartment complex to identify reed species, their density, and potential ecological impacts. It finds the invasive Phragmites australis in nearly all areas, which threatens native plants and wildlife. While cattails remain in some regions, the document predicts the Phragmites will continue expanding and outcompeting cattails. It recommends treatment methods to prevent further spread of Phragmites.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms for those who already suffer from conditions like anxiety and depression.
April is Parkinson’s Awareness Month and it’s an ideal time to take a look at your estate plan to ensure you’ve made accommodations should you or a loved one is diagnosed.
Política Regulatoria en el Perú - Uniendo el marco para la calidad regulatoriaPaulo Pantigoso
Este documento resume un estudio de la OCDE sobre la política regulatoria en Perú. El estudio encuentra que aunque Perú ha tenido un fuerte crecimiento económico recientemente, todavía carece de una política regulatoria integral. El estudio recomienda que Perú establezca un órgano supervisor para coordinar las actividades regulatorias actualmente dispersas, así como para introducir nuevas herramientas como un sistema formal de evaluación de impacto regulatorio y una política de cumplimiento regulatorio. El estudio también recomienda mejorar la coordinación entre los niveles
This document describes a student's experience developing a personal learning network (PLN) using Twitter in an education course. It discusses how the student initially struggled to understand the concept of a PLN but began following educators, organizations, and experts in literacy, technology, and general education. Over time, the student's network grew and they organized contacts into lists for easier access to information. While the PLN provided valuable resources and insights, it also presented challenges with information overload and time management. The student reflected on how their PLN is enhancing their knowledge and shifting their TPACK framework. Overall, the PLN exposed the student to new ideas and viewpoints as they continue developing their network and skills.
If you're an adult, there’s a place for proper planning to ensure your assets pass down and your liabilities are addressed.To learn more about Estate Planning in New Hampshire in this presentation.
The Effects Of Fire And Flooding On The Florida EvergladesJessica Tanner
The document is a research paper about the effects of fire and flooding on tree island communities in the Florida Everglades. The author hypothesizes that flooding shortly after a fire will have a positive effect by providing resources carried by floodwaters to aid healthy growth following the fire. Tree islands are essential to Everglades landscape and biodiversity, varying in size and species. The paper will examine how different conditions like fire and flooding affect the tree island communities.
This document summarizes a study of waterfowl diversity at Lake Reba in Madison County, Kentucky during fall migration. The author surveyed the lake in October, November, and early December, recording 11 total waterfowl species present. The four dominant species were American Coots, Mallards, Canadian Geese, and Pied-billed Grebes. Diversity indexes showed low diversity between waterfowl species across the survey months.
This document examines factors affecting fish entrainment at the massive water diversions of the State Water Project and Central Valley Project in the San Francisco Bay Delta estuary. It analyzes 13 years of data on fish salvage counts, pumping operations, and environmental characteristics to determine what factors influence entrainment of different fish species. Entrainment of migratory pelagic species like delta smelt, longfin smelt, and striped bass was found to correlate with their seasonal occurrence near the export facilities. Flow patterns through the estuary also predicted pelagic fish entrainment. Entrainment of resident demersal species and littoral species was not clearly linked to diversion flows. The study suggests manipulating hydrodynamics
This document summarizes a presentation by Ryan Wersal on alligatorweed, an invasive aquatic plant species. It discusses alligatorweed's origins in South America and impacts as a nuisance species worldwide. The presentation describes alligatorweed's identification features, habitat, distribution in the US, ecological impacts including reduced water quality and access, and management methods such as biological control using beetles or moths and chemical control with herbicides. Contact information is provided for Ryan Wersal as an expert on alligatorweed management.
This study analyzed the stomach contents and stable isotope ratios of over 960 juvenile fish and their potential food sources from pelagic and littoral habitats in the tidal freshwater region of the San Francisco Estuary. The results showed evidence of two predominant food web pathways. Pelagic fish and some littoral fish relied on a zooplankton-phytoplankton trophic pathway, while the majority of littoral fish had diets and carbon isotope ratios consistent with energy from submerged aquatic vegetation and epiphytic macroalgae. Analysis with a mixing model revealed that littoral fish obtained the overall majority of their nutrition from consuming grazer amphipods. Examining both stable isot
The document discusses the range dynamics of the invasive zebra mussel in North America. It describes several hypotheses for the main drivers of zebra mussel range expansion, including recreational boating, environmental conditions, dispersal within connected water bodies, and the role of dams and impoundments. The document also examines debates around limitations to zebra mussel populations from factors like food availability and suitable substrate. Overall, it argues that the range dynamics of zebra mussels result from both human activities and environmental conditions, not just one or the other.
This document summarizes a study that compared the habitat structure, invertebrate assemblages, and fish diets associated with patches of the native floating plant pennywort versus the introduced floating plant water hyacinth in the Sacramento-San Joaquin Delta of California. The study found several key differences between the two plants: 1) pennywort patches had higher leaf and insect densities and different insect assemblage compositions than hyacinth patches; 2) hyacinth roots in the water column had significantly more surface area than pennywort roots; and 3) densities and taxonomic compositions of aquatic invertebrates generally differed between the two plant types. The introduction of water hyacinth caused significant ecological alterations to the surrounding community
This study examined three species of aquatic freshwater turtles in Costa Rica for haemogregarine infections. All turtles sampled were positive for intraerythrocytic haemogregarines, representing the first report of these parasites in turtles from Central America. Black river turtles had a significantly higher average parasitemia (0.34%) than white-lipped mud turtles (0.05%). Parasites in the single scorpion mud turtle examined were smaller and did not displace the host cell nucleus like those in the other two species. This is the first report of haemogregarines in the white-lipped mud turtle, scorpion mud turtle, and any Rhinoclemm
(FINAL) ROUGH DRAFT FOR SENIOR RESEARCH Jennifer Edit 4-14-15Jennifer Cherry
This document is a senior research paper that analyzes temporal and spatial trends in sea turtle strandings and nesting in Volusia County, Florida from 1989-2012. It finds that sea turtle strandings in Volusia County have increased over time and are correlated with increases in both the county and state human populations. Strandings are dominated by loggerhead and green sea turtles. Despite rising strandings, nesting numbers have also increased, likely due to the county's aggressive nest protection programs. The analysis aims to better understand relationships between strandings, nesting, human activities, and environmental factors like temperature to inform sea turtle conservation efforts.
BiologyYou will respond to your classmates posts and add sometChantellPantoja184
Biology:
You will respond to your classmates' posts and add something new. The response is broad this week, but I encourage you to discuss your opinions and thoughts. Science isn't set in stone. The 'helpers in the nest' theory is controversial, even among evolutionary biologists, as are many topics in this category. BUT DON’T FORGET TO CITE THEM. (Respond with a 100 Words for Each)
First Post:
Invasive species can be any kind of living organism not native to an ecosystem that causes harm. This can be to the environment, human health, or the economy. These species typically grow and reproduce quickly and tend to spread aggressively. Now, when I think of an invasive species the first thing that comes to my mind is the iguana. Not entirely sure why, maybe its because they are all over nsu's campus, but it was interesting to google other invasive species and learn more about them.
I researched the European Green Crab. The European green crabs are considered one of the most widespread invasive marine species on the planet! They began invading Washington state in 1996. The crabs themselves are native to Europe and North Africa. They were first brought to North America in 1817 by being carried in the holds of wooden ships. It is thought that they were spread during their long larval stage which lasts up to 90 days. They would spread via shipping on boats or by drifting on ocean currents. They also frequently move from one area to another by "hitchhiking" on boats, in gear, or in packaged shellfish.
When the green crab population grows too large, they cause various issues. They compete with other shellfish, destroy eelgrass that is an important habitat for Dungeness crabs and salmon, and disturb sediment. They are able to out- compete native species because they live 4-7 years, the eat a wide variety of plants and animals, and the females release 185,000 eggs up to twice a year. It is said that once the European Green Grab establishes a population in a particular area, it is practically impossible to get rid of them. Groups and organizations are working towards limiting their spread and limiting the ensuing damage.
References:
https://www.invasivespeciesinfo.gov/aquatic/invertebrates/european-green-crab (Links to an external site.)
https://www.dfo-mpo.gc.ca/species-especes/profiles-profils/europeangreencrab-crabevert-eng.html (Links to an external site.)
https://www.nwf.org/Educational-Resources/Wildlife-Guide/Threats-to-Wildlife/Invasive-Species
Second Post:
Reading about different types of invasive species is interesting especially considering the major changes they cause within an ecosystem. Information regarding the Burmese Python was quite striking. The python originates from southeast Asia and has made a significant impact on the ecosystem of the Everglades in South Florida. There are two speculations about how the burmese python reached the Everglades. Similarly to Professor Kiene's mention of the pleco and tiger oscar, ...
Extinct species of animals from India were discussed. Key extinct species included the Zanzibar leopard, Baiji river dolphin, and Indian cheetah. The main causes of extinction were loss of habitat due to human activities like agriculture, overhunting, and pollution. Conservation efforts in India and internationally include establishing marine protected areas and legislation to protect threatened wildlife. However, human factors continue to threaten biodiversity if not addressed.
The Delta smelt is an endangered fish species endemic to the California Bay Delta region. It serves as an important ecological indicator of environmental conditions in the Delta. However, the smelt population has declined dramatically due to water diversions that have reduced and degraded its freshwater habitat. Conservation efforts to protect the smelt under the Endangered Species Act have caused conflicts with water users. Solutions proposed to help recover the smelt population include reassessing water allocations and enacting proactive management strategies to protect dependent species.
This document analyzes sea turtle strandings in Louisiana over an eight year period from 2002 to 2009. A total of 163 sea turtles from 5 different species were recorded as strandings, with concentrations primarily in the Lake Charles area and along Grande Isle and Grand Terre. Strandings peaked in late April through early June and again in early October through mid-November, overlapping with periods of recreational boating and open fisheries seasons for menhaden and shrimp. About 23% of turtles showed obvious strike marks. A chi-squared test found a statistically significant association between strandings and open fisheries seasons, though this does not imply fishing caused the observed morbidity and mortality.
This document provides a management plan for mute swans in New York State. The plan aims to eliminate free-ranging mute swan populations in the state by 2025. Mute swans are an invasive species that were introduced in the late 1800s and their population has grown to around 2,200 birds. The plan outlines several strategies to achieve its goal, including increasing public education about mute swans, prohibiting their import/propagation, preventing releases of captive birds, encouraging control in neighboring areas, and allowing hunting and other forms of take to actively reduce wild populations.
California Mussels Influence On Mytilus CalifornianusStacey Wilson
The document discusses how human activities affect ocean tides and estuaries. Estuaries are partially enclosed bodies of water where freshwater from land meets saltwater from the sea, making salinity and water level dependent on ocean tides. Human activities like agriculture, waste disposal, and land development have increased erosion and altered river flows into estuaries, accelerating their aging. This redirects sediments and changes water circulation, salinity, and biological communities in estuaries. Coastal development and ports have also disrupted natural shorelines and water circulation.
This study analyzed data on the abundance of white shrimp, brown shrimp, spotted seatrout, red drum, and southern flounder in Texas coastal bays from 1987 to 2014 to investigate potential predator-prey interactions between these species. Catch per unit effort data were obtained from fishery surveys and analyzed using co-integration and linear regression methods. The preliminary results found a statistically significant interaction between white shrimp and southern flounder abundance, suggesting white shrimp serve as an important forage species for southern flounder and their population dynamics may be linked. Further analysis is still needed to quantify the direction and strength of these interactions.
1) The document analyzes acoustic data collected between 2008-2013 from three zones within Laguna San Ignacio, Baja California Sur, Mexico where gray whales breed each winter.
2) The zones differ in levels of whale usage and tourist activity, with the upper zone used mostly for birthing and the lower zone used for whale watching tours.
3) Acoustic distributions were computed and compared across years and zones. The upper zone is dominated by snapping shrimp noise with a daily cycle, while the middle and lower zones have additional noise from tourist boats during daylight hours.
This document provides an overview of the Atlas of the Mammals of Ontario. It was created through the collection of distribution data from institutions and volunteers. Species accounts and range maps are provided for Ontario's 86 wild mammal species. The maps show mammal records plotted within grid squares, with symbols indicating the time period of the record. The atlas aims to document the current distribution of mammals in Ontario and identify areas needing more research. It is intended to aid conservation efforts and environmental assessments.
Lloyst et al 2015 (nearshore habitat stocked eel)Megan Lloyst
This document summarizes a study that characterized nearshore habitat associations of stocked American eel (Anguilla rostrata) in Lake Ontario and the upper St. Lawrence River. The study found that eel presence was positively associated with soft substrate in spring and rubble substrate in fall. Habitat preferences changed with eel size, with smaller eels preferring coarse substrates and larger eels preferring silt substrates in deeper water. The available habitats differed between stocking locations, providing a mix of coarse and fine substrates. The stocked eels utilized various habitats, demonstrating ontogenetic shifts in habitat use.
Saarela JM, LJ Gillespie, PC Sokoloff. The Arctic Flora of Canada and Alaska project. Arctic Change 2014, 8–12 December 2014, Ottawa, ON, Canada. [poster]
Similar to Reed et al 2016 Herpetologica NeFa in Machado Lake-2 (20)
Reed et al 2016 Herpetologica NeFa in Machado Lake-2
1. Ecology and Control of an Introduced Population of
Southern Watersnakes (Nerodia fasciata) in Southern California
ROBERT N. REED
1,5
, BRIAN D. TODD
2
, OLIVER J. MIANO
2
, MARK CANFIELD
3
, ROBERT N. FISHER
4
, AND LOUANNE MCMARTIN
3
1
U.S. Geological Survey, Fort Collins Science Center, 2150 Centre Avenue, Building C, Fort Collins, CO 80526, USA
2
Department of Wildlife, Fish and Conservation Biology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
3
U.S. Fish and Wildlife Service, Pacific Southwest Region, 850 S. Guild Avenue, Suite 105, Lodi, CA 95240, USA
4
U.S. Geological Survey, 4165 Spruance Road Suite 200, San Diego, CA 92101-0812, USA
ABSTRACT: Native to the southeastern United States, Southern Watersnakes (Nerodia fasciata) are known from two sites in California, but their
ecological impacts are poorly understood. We investigated the ecology of Southern Watersnakes in Machado Lake, Harbor City, Los Angeles
County, California, including an assessment of control opportunities. We captured 306 watersnakes as a result of aquatic trapping and hand
captures. We captured snakes of all sizes (162–1063 mm snout–vent length [SVL], 3.5–873.3 g), demonstrating the existence of a well-established
population. The smallest reproductive female was 490 mm SVL and females contained 12–46 postovulatory embryos (mean 5 21). Small
watersnakes largely consumed introduced Western Mosquitofish (Gambusia affinis), while larger snakes specialized on larval and metamorph
American Bullfrogs (Lithobates catesbeianus) and Green Sunfish (Lepomis cyanellus). Overall capture per unit effort (CPUE) in traps declined
with time during an intensive 76-d trapping bout, but CPUE trends varied considerably among traplines and it is unlikely that the overall decline in
CPUE represented a major decrease in the snake population size. Although we found no direct evidence that Southern Watersnakes are affecting
native species in Machado Lake, this population may serve as a source for intentional or unintentional transportation of watersnakes to bodies
of water containing imperiled native prey species or potential competitors.
Key words: Diet; Fat body mass; Invasive species; Los Angeles; Reproduction; Trap success
WHEN MOST herpetologists think of invasive snakes, Brown
Treesnakes (Boiga irregularis) and Burmese Pythons (Python
molurus bivittatus or P. bivittatus) are likely to come to mind.
The former has eliminated most birds from the island of Guam
since its accidental introduction about 50 yr ago (Savidge 1987),
whereas the latter is a more recent introduction to southern
Florida, USA, and appears to have caused major reductions in
native mammal populations (Dorcas et al. 2012; McCleery et al.
2015). As snakes go, these two species are dissimilar in ecology
and in the ecosystems into which they were introduced, but they
are similarly notable in terms of their impacts and in that they
have garnered extensive media attention. Several other species
of snakes have established nonnative populations around the
globe, however, and the number of known introductions of
exotic snakes has increased exponentially in recent decades
(Kraus 2009). The frequency and taxonomic diversity of
introductions suggest a future in which additional populations
of introduced snakes will become established.
The introduction of watersnakes of the genus Nerodia into
parts of western North America has generated interest in them as
potentially invasive species (Rose et al. 2013). The genus includes
10 semiaquatic species in North America with native distributions
east of the Rocky Mountains (Ernst and Ernst 2003). They feed
on a wide array of aquatic vertebrates, particularly fish and frogs
(Mount 1975; Ernst and Ernst 2003; Gibbons and Dorcas 2004).
In western North America, many freshwater fishes and
amphibians are in decline and are protected as threatened and
endangered species, or are of conservation concern (Fisher and
Shaffer 1996; Moyle et al. 2011). This has generated concern
about possible impacts of nonnative watersnakes on native
species that might serve as prey (Miano et al. 2012). Additionally,
west of the Rocky Mountains, gartersnakes (genus Thamnophis)
have radiated to reach their peak diversity and occupy many of
the semiaquatic niches occupied by watersnakes in eastern North
America (Rossman et al. 1996). Several species of Thamnophis
are listed on federal or state endangered species lists or are
otherwise considered species of conservation concern. A recent
study found that large parts of western North America have
suitable climate and habitat capable of supporting nonnative
populations of Common Watersnakes (N. sipedon) and Southern
Watersnakes (N. fasciata), and identified several species of fish,
amphibians, and gartersnakes that could be at risk from nonnative
watersnakes (Rose and Todd 2014). For these reasons, it is
important to understand the distribution, ecology, and potential
for controlling exotic populations of nonnative watersnakes.
Southern Watersnakes are native to the southeastern
United States, where they are distributed along the Coastal
Plain from North Carolina to eastern Texas and throughout
Florida (Gibbons and Dorcas 2004). Among at least four
introductions of three species of Nerodia to the State of
California (Balfour and Stitt 2008; Rose et al. 2013) are two
populations of N. fasciata. One population has been known
from the vicinity of Folsom, near Sacramento, for .20 yr
(Balfour and Stitt 2002; Stitt et al. 2005; Balfour et al. 2007).
The second was first reported in 2006 from Machado Lake in
Ken Malloy Harbor Regional Park, Harbor City, California,
in the southwestern part of greater Los Angeles (Fuller and
Trevett 2006). The population status of the Harbor City
population is largely unknown. The purpose of our study
was to assess the status and ecology of the Harbor City
population, evaluate the feasibility of eradication, and gain
a better understanding of the potential impacts of these exotic
snakes in an urban habitat.
MATERIALS AND METHODS
Study Site
Machado Lake is a shallow impoundment of ,16-ha
surface area in Ken Malloy Harbor Regional Park (97 ha5
CORRESPONDENCE: e-mail, reedr@usgs.gov
Herpetologica, 72(2), 2016, 000–000
E 2016 by The Herpetologists’ League, Inc.
0
2. including the lake; Fig. 1). The lake receives runoff and
stormwater from a 6300-ha urban drainage via the channelized
Wilmington Drain (formerly the Bixby Slough), as well as
from several stormwater drains. As a result, the lake is con-
sidered impaired by bacteria, ammonia, copper, and lead
(City of Los Angeles 2014). Depending on the season and
intensity of recent vegetation-control efforts, as much as
a third of the lake can be densely covered in exotic Water
Primrose (Ludwigia sp.). Native Tule Bulrush (Scirpus spp.)
and exotic Cattail (Typha spp.) are also common along the
margins of the lake. Although heavily polluted, the park
harbors remnants of native riparian forest and freshwater
marsh that have largely been eliminated from the rest of Los
Angeles County. As a recipient of urban runoff and lacking
any surface flow outlet to the nearby Port of Los Angeles,
Machado Lake is generally isolated from other water bodies.
This reduces the odds that individual watersnakes will
disperse without human intervention to other areas with
higher numbers of native species that would serve as prey,
including species of conservation concern. Among nearby
aquatic systems, the heavily channelized and intermittent
Dominguez Channel (5.5 km away) and Los Angeles River
(8.2 km away) lie to the east; to the west, extensive hills
separate Machado Lake from the Agua Amarga reserve
(10 km away).
Capture Methods
We trapped snakes in Machado Lake using a mix of plastic
(Model 700, Gator Buckets) and metal (Gee’s minnow trap,
Tackle Factory) traps. We widened the openings of the metal
FIG. 1.—Aerial photo of Machado Lake and surrounding areas, Harbor City, California, USA (inset). Ephemeral wetlands mentioned in text are located
south and southwest of the baseball diamond visible in the photo area. A color version of this figure is available online.
0 Herpetologica 72(2), 2016
3. traps from 2.5-cm to 3.0–3.5-cm diameter, because this pro-
motes higher capture rates of large-bodied snakes (Willson
et al. 2008). We set traps such that the entire funnel apex
was submerged, but the top of the trap was above water
to allow captured animals access to air. The traps were
self-baiting with Western Mosquitofish (Gambusia affinis)
and other potential prey items (Winne 2005). Depending
on density of aquatic vegetation, traps were either placed
directly in floating vegetation or were attached to bamboo
stakes to prevent them from sinking. Traps were placed in
linear or sinuous arrays through or on the edge of aquatic
vegetation (primarily Ludwigia) in water depths of 0.25–
1.5 m, and were checked daily by biologists on foot or in a
kayak. To assess whether drift fences increased capture rate,
we erected three drift-fence arrays in Summer 2010 using
plastic erosion-control fabric equipped with stakes, ensuring
that $20 cm of the fence was out of the water and $30 cm
was submerged. Each fence was 8 m long, with 2 plastic
and 2 metal traps on each side (8 traps per fence). As
controls for the fences, we placed an equivalent number
and composition of traps 10 m from the fence in similar
microhabitat and water depth. We also conducted a limited
amount of nocturnal visual searching on foot in shallow areas
of the lake, using headlamps to locate snakes and capturing
them by hand. Because management agencies requested
that all captured snakes be removed, we were not able to
conduct mark–recapture analysis to obtain a rigorous esti-
mate of population size. Sampling occurred on multiple
occasions over 2 yr, as follows: 22–30 September 2009
(920 trap-nights), 30 April–7 May 2010 (1099 trap-nights),
and 6 July–19 September 2010 (13,335 trap-nights). We
conducted 150 trap-nights of sampling in the Wilmington
Drain, as well as limited sampling in two shallow and
intermittent ponds ,500 m southeast of Lake Machado
(150 trap-nights, 5 person-hours of visual surveys; these
ponds can be seen south of the baseball diamond in Fig. 1).
All snakes were euthanized with an overdose of inhalant
Isoflurane within 24 h of capture. Snakes captured in
2009 were necropsied immediately after euthanasia, whereas
those captured in 2010 were necropsied after having been
frozen for 5–8 mo. We weighed and measured all snakes
during necropsy, examined gastrointestinal tracts for prey
items, and recorded evidence of previous injuries (scars,
etc.). Snakes captured during May–September of 2010 were
subjected to more intensive necropsy, including removing
and weighing fat bodies, counting the number of follicles or
embryos in females, and measuring the largest and smallest
follicles in females.
We used chi-square tests to assess goodness of fit between
observed and expected values. We used the Shapiro–Wilk
test to assess normality of distributions. When assumptions
of linear models were met, we used unpaired two-tailed
t-tests to examine whether means of two groups were
statistically different from one another. When assumptions of
linear models were not met, we used the Kruskal–Wallis
nonparametric equivalent of one-way analysis of variance to
test for difference between two or more groups of response
variables. We used linear regression to examine the effect
of time on both capture per unit effort (CPUE; traps only)
and volume of the largest follicle in reproductive females,
and Pearson product-moment correlation analysis to exam-
ine relationships between fat body mass and body length.
Descriptive statistics and analyses were calculated in
SYSTAT v13 (Systat Software, Inc.) and Microsoft Excel
(Microsoft Corporation). We set a 5 0.05 for all statistical
analyses; values are presented as means 61 SD.
RESULTS
Body Size and Capture Rate
We captured 306 Southern Watersnakes, including 47
in September 2009, 62 in May 2010, and 197 during July–
October 2010, consisting of 275 trap captures and 31 hand
captures. Of these 306 individuals, 303 were from Machado
Lake and 3 were from the Wilmington Drain. We received
an additional 5 snakes trapped between 26 September and
1 October 2010 in Wilmington Drain from a collaborator.
We detected no snakes in the ephemeral ponds to the
southeast of Machado Lake by either traps or visual surveys.
The mean snout–vent length (SVL) of snakes captured
in plastic traps was 461 6 145 mm (range 5 168–980 mm),
slightly smaller than the mean size of snakes captured in
metal traps (481 6 148 mm, range 5 224–880 mm). Snakes
captured during visual surveys averaged 437 6 207 mm
(range 5 162–1023 mm). There was no difference in SVL as
a function of capture method (Kruskal–Wallis H 5 2.04,
df 5 2, P 5 0.36). Drift fences did not increase snake
capture rates because we captured 30 snakes using traps
along drift fences and 21 in the adjacent control traps
(x2
5 1.59, df 5 1, P 5 0.21). Among all snakes, 4.6%
exhibited scars or other signs of previous injury. Not all
variables could be recorded for every snake; therefore,
sample sizes vary in results given below.
During the intensive trapping effort in 2010, we deployed
12 trap arrays in Machado Lake for various lengths of time.
Overall CPUE during this period was 0.019 snakes per trap-
night, and ranged from 0.009 to 0.062 across the 12 arrays.
CPUE declined during the course of the trapping effort
when calculated as the effect of trapping week on overall
mean CPUE across trap arrays (linear regression, r2
5 0.77,
m 5 20.003, b 5 0.046, P , 0.01).
Size and Sex
Among all captured snakes, body size averaged 456 mm in
SVL and 130 g in mass. Females attained larger body sizes
than did males (Table 1; Fig. 2), although only mass was
statistically different when considering animals of all
size classes (SVL, t 5 0.85, df 5 236, P 5 0.40; mass, t 5
4.03, df 5 236, P , 0.001). Among individuals .500 mm in
SVL (reproductively mature), however, females were longer
(t 5 3.59, df 5 124, P , 0.001), and the largest female
was more than twice the mass of the largest male. The six
smallest individuals, presumably recent neonates, averaged
170.7 mm in SVL and 4.1 g in mass (ranges 5 162–185 mm
and 3.5–4.8 g, respectively). Relative tail length (tail length
divided by total length) was greater in males than in females
(0.27 vs. 0.24, respectively; t 5 213.78, df 5 186, P , 0.001;
Table 1). We captured more females (187) than males (119)
for a ratio of 1.57:1 that differed from 1:1 (x 2
5 15.1, df 5 1,
P , 0.001). We were unable to quantify variation in capture
probability by sex (e.g., Tyrrell et al. 2009) and also
funnel traps have known size biases in capture probabilities
(Willson et al. 2005, 2008); therefore, this ratio is not
necessarily representative of the overall population.
REED ET AL.—ECOLOGY OF NONNATIVE NERODIA 0
4. Reproduction
Reproductive data were collected from female snakes
captured during the July–September 2010 trapping bout.
Among females .490 cm in SVL captured in July (n 5 33),
when embryos should be most apparent during necropsy,
42% contained embryos. The smallest female with embryos
was 490 mm in SVL and 128 g in mass, while the largest was
766 mm and 675 g. Among 90 females .490 mm in SVL,
28 (31%) contained developing embryos while another
31 (34%) contained visible follicles. Mean litter size was
21.16 6 1.75 (range 5 12–46) among 26 females in which
the number of embryos could be counted. During Summer
2010, volume of the largest postovulatory embryo increased
over time (females with measured embryos captured
3 May through 1 September; linear regression r2
5 0.20,
b 5 215, m 5 0.41, P 5 0.03). The smallest juvenile snakes
(, 250 mm in SVL, n 5 31) were generally captured in
August and September regardless of sampling year.
Fat body mass was positively correlated with SVL (Pearson
product-moment correlation, r 5 0.76; Fig. 3) across all
snakes. Over the course of the 2010 summer sampling season,
female snakes of reproductive size (.490 mm SVL; n 5 63)
exhibited a weak positive correlation between relative fat
body mass (fat mass divided by total mass) and date of
capture (r 5 0.12), with a wide range of fat body masses late
in the sampling period. Using the same size cut-off for males
(n 5 27) yielded a weaker relationship between these
variables (r 5 0.05) over the course of the sampling period.
Diet
Prey identified from snakes captured during visual surveys
included Western Mosquitofish, Green Sunfish (Lepomis
cyanellus), and a single Brown Bullhead (Ameiurus nebulosus);
29% of hand-captured individuals contained prey. Prey
identified from snakes captured in traps included G. affinis,
L. cyanellus, and tadpoles and small metamorphs of American
Bullfrogs (Lithobates catesbeianus). Snakes ,400 mm in SVL
contained only G. affinis, except for one snake (SVL 5 393
mm) that had consumed a bullfrog tadpole; 33% of these
small snakes contained identifiable prey. Among snakes
.400 mm in SVL, L. catesbeianus was more prevalent among
gut contents (51.4% of identifiable prey) and G. affinis
became less prevalent (not observed among snakes . 580
mm). Among the 10 largest snakes (720–1023 mm in SVL),
identifiable prey included L. catesbeianus (n 5 5), Lepomis
cyanellus (n 5 4), and the bullhead. Overall, 32% of trapped
snakes contained identifiable prey (Table 2).
DISCUSSION
Our results support the conclusion that Machado Lake
is home to a large population of Southern Watersnakes,
including all size classes and many reproductive individuals.
We do not know how long Southern Watersnakes have
been established in Machado Lake. A single individual was
reported from “a pond in west Los Angeles” in 1976 (Bury and
Luckenbach 1976:8), but Fuller and Trevett (2006) presented
evidence that this observation might have been from
a different park in Long Beach. The pet trade is suspected
as being the most likely introduction pathway for the
Machado Lake population because Southern Watersnakes
have long been listed on wildlife dealers’ price lists
and because it seems relatively unlikely that an aquatic snake
from the southeast United States would be unintentionally
transported to a lake in southern California via cargo,
aquaculture, or by other means. Snakes of the genus Nerodia
TABLE 1.—Summary statistics of body sizes of Southern Watersnakes (Nerodia fasciata) captured from Machado Lake, Harbor City, California, USA. Tail
lengths were omitted from analysis for 58 individuals (28 females, 30 males) with stub tails. Means are reported 61 SD. Sample sizes are reported after
ranges, and vary because not all variables were recorded for all individuals.
Mass (g) Snout–vent length (mm) Tail length (mm)
Mean Range Mean Range Mean Range
Overall 130.0 6 137.6 3.5–873.3 (n 5 306) 456.1 6 150.3 162–1023 (n 5 306) 147.4 6 43.5 58–254 (n 5 248)
Females 149.2 6 163.3 4–873.3 (n 5 187) 463.7 6 165.8 170–1023 (n 5 187) 144.0 6 45.9 58–254 (n 5 159)
Males 100.7 6 74.4 3.5–390.7 (n 5 119) 444.2 6 121.6 162–747 (n 5 119) 153.4 6 38.5 65–232 (n 5 89)
FIG. 2.—Scatterplot of mass as a function of snout–vent length for female
(open squares) and male (filled diamonds) Nerodia fasciata removed from
Machado Lake, Harbor City, California, USA.
FIG. 3.—Scatterplot of relative fat mass (fat body mass divided by total
body mass) as a function of collection date for adult female (open diamonds,
n 5 63) and male (filled squares, n 5 27) Nerodia fasciata (.490 mm SVL)
removed from Machado Lake, Harbor City, California, USA, during the
2010 sampling period.
0 Herpetologica 72(2), 2016
5. have been regulated as a restricted species by the California
Department of Fish and Game since 2008, and importation,
transportation, possession, and sale are now prohibited
without a special permit. All four introductions of Nerodia
into California are known to have occurred prior to this
restriction being implemented.
One of our goals was to assess whether trapping and
hand captures would appreciably reduce the overall popula-
tion of Southern Watersnakes in Machado Lake. Overall,
90% of our sample was captured in aquatic traps. Nocturnal
visual surveys were relatively successful (,1 snake captured
per search hour), but we curtailed visual surveys after 30
person-hours for safety reasons at the suggestion of local law
enforcement personnel. Although traps along drift fences
captured ,50% more snakes per trap-night than did the
adjacent unfenced arrays, the sample size of captures was too
small for robust conclusions and the fences required regular
maintenance, especially after windy days and water-level
changes. The reluctance of local management agencies to
allow release of any captured snakes meant that we were
unable to assess efficacy of control efforts via mark–
recapture, forcing us to rely on CPUE as an index of changes
in population density. We observed an overall decline in
mean CPUE over time during the Summer 2010 intensive
trapping effort, and it is tempting to infer that our efforts
were effective in reducing overall snake densities in Machado
Lake. If this were the case, we would expect CPUE of
each array to mirror the overall trend, but our results did
not support this prediction. Intensive snake trapping
(86 traps/ha) in an isolated wetland in South Carolina
yielded a minimum density of 76 Southern Watersnakes per
ha (Willson et al. 2011); the density of introduced Common
Watersnakes in a northern California wetland was estimated
at 56/ha (Rose et al. 2013). In contrast, over 76 d in 2010, we
removed only 12 snakes/ha in a 16-ha lake with a trapping
intensity that never exceeded 11 traps/ha. Combined with low
initial probabilities (0.02–0.05) of trap capture for Southern
Watersnakes in South Carolina (Willson et al. 2011), and the
fact that about one-third of trapped Southern Watersnakes
escape from traps (Willson et al. 2005), these comparative
results suggest that our sample of snakes from Machado Lake
represented a small proportion of the total population size.
Our discussion of the body sizes and sex ratio of captured
snakes must be prefaced by acknowledging that both trap and
hand captures are almost certainly biased by varying
detection probabilities among size classes, ages, and sexes.
These biases are widespread among snake studies (e.g.,
Tyrrell et al. 2009), and are established for watersnakes
including N. fasciata (Willson et al. 2008, 2011). Such caveats
about detection probabilities also apply to most of the
historical literature with which we can compare our results
(although this bias was largely unappreciated in historical
literature), reducing our confidence in the strength of com-
parisons. Overall, our results were not highly divergent from
those found for populations in the native range. Presumptive
neonates at Machado Lake averaged 170 cm in SVL and 4 g in
body mass, similar to sizes of captive-born Southern Water-
snakes reported by Scudder-Davis and Burghardt (1996).
Means of both mass and SVL were lower in the Machado
population compared with a native population in South
Carolina (SC; female mass 5 149 g in Machado vs. 246 g in
SC; male mass 5 100 g in Machado vs. 113 g in SC; female
SVL 5 456 mm in Machado vs. 638 mm in SC; male SVL 5
444 mm in Machado vs. 535 mm in SC; Semlitsch and
Gibbons 1982). The South Carolina study included no recent
neonates, however, thus skewing means toward larger
sizes. The maximum values for snakes from the Machado
population were larger than the maxima for those from South
Carolina for all but female mass: 873 g (Machado) vs. 990 g
(SC). Our smallest pregnant female was 490 mm in SVL,
smaller than the minimum size of 550 mm reported from the
native range in Louisiana (Kofron 1979).
The largest female in our data set (captured by hand) was
longer than any of the Southern Watersnakes captured
during multiple years of sampling in South Carolina (J.D.
Willson, personal communication); on several occasions, we
observed even larger and apparently gravid females basking
on floating debris in Machado Lake. These snakes were
larger than any snake captured in minnow traps, emphasiz-
ing the size-specific variability in trap-capture rates across
sizes and sexes, and implying that our estimates of re-
productive capacity might have been considerably higher if
these animals had been included in our necropsy data set. If
the largest gravid females are aphagic and sedentary during
late gestation, then neither intercept (i.e., drift fences with
traps) nor attractant (self-baiting with prey) traps are likely
to be effective. Removing available surface debris in the lake
and replacing it with basking traps (Vogt 2012) especially
designed to capture and retain snakes might be a more
effective means of removing this demographically important
segment of the snake population.
Small, postovulatory embryos were detected in four females
captured during May 2010, implying that vitellogenesis likely
occurred in spring. Embryo sizes increased markedly among
snakes captured in July and August, and the smallest snakes
were found in August and September, indicating that
parturition occurred during this period. These patterns are
similar to vitellogenesis and parturition dates in the native
range (Kofron 1979; Lorenz et al. 2011). Among females
.490 cm in SVL captured in July (n 5 33), when embryos
should be most apparent during necropsy, 42% contained
embryos. Furthermore, our observation that female fat body
mass exhibited wide variation starting in early September also
indicates that parturition occurred during this period, but that
not all adult females in the population had reproduced.
Female reproduction might therefore be less frequent than
once per year (possibly biennial) at Machado Lake. In a study
of another invasive population of Southern Watersnakes
TABLE 2.—Summary of diet of four size classes of Nerodia fasciata
captured in Machado Lake, Harbor City, California, USA, as evidenced by
prey removed from snake digestive tracts. We categorized “postlarval”
Lithobates catesbeianus as any individual with well-developed forelimbs,
regardless of the presence of a tail. See text for caveats about potential bias
introduced by including snakes removed from self-baiting traps.
Snout–vent length (mm)
Diet #250 251–500 501–750 $751
Total n 31 149 119 7
Number (%) containing prey 7 (23%) 52 (35%) 51 (43%) 7 (100%)
Prey species
Gambusia affinis 7 34 5 0
Ameiurus nebulosus 0 0 0 1
Lithobates catesbeianus (larval) 0 2 4 0
L. catesbeianus (postlarval) 0 8 20 3
REED ET AL.—ECOLOGY OF NONNATIVE NERODIA 0
6. near Folsom, California, 85% of captured adult females were
gravid (Stitt et al. 2005). It is not possible to discern whether
the Folsom population has high reproductive success or
whether basking pregnant females are particularly vulnerable
to hand capture (the method that yielded the most snakes in
that study). Our observed mean litter size (21; based on
number of oviductal embryos) is similar to mean values
reported for both native (Semlitsch and Gibbons 1982; Palmer
and Braswell 1995; Ernst and Ernst 2003) and introduced
(Stitt et al. 2005) populations, and our observed maximum of
46 embryos underscores the potential for new extralimital
populations to be established based on introduction of even
a single, large, pregnant female of this species.
Southern Watersnakes are known to be generalist feeders,
with .40 prey taxa reported in the literature (Ernst and
Ernst 2003; Gibbons and Dorcas 2004). Our necropsies
revealed only four prey species consumed, predominantly
G. affinis and Lithobates catesbeianus, with lower prevalence
of sunfish. These results are similar to those reported for
Southern Watersnakes from Louisiana by Mushinsky et al.
(1982), who noted an ontogenetic dietary shift in which
small snakes eat fish (primarily G. affinis), whereas larger
individuals switch to frogs and larger fish species (including
sunfish and catfish). Dietary data from snakes captured in
traps are probably biased because of the occasionally high
densities of prey species that accumulate in traps over the
course of a day. We sometimes captured dozens of bullfrog
tadpoles and hundreds of mosquitofish in a single trap, and
we recorded up to 17 mosquitofish inside trapped snakes but
not more than two in hand-captured snakes. Therefore,
although our results might have captured the species
composition of the snake diet, the number of individual
prey items in a snake was biased by the method of capture.
We did not capture or observe any fish, frogs, or snakes
native to California during our snake trapping efforts, visual
surveys, or day-to-day tasks at Machado Lake, nor did we
find any native species inside watersnakes during necropsies.
Instead, we encountered a wide range of introduced aquatic
fauna in the lake and in snake stomach contents, making it
difficult to assess the potential ecological impacts of this
exotic watersnake population. It is unsurprising that a snake
native to the southeastern United States was able to become
established in a lake already occupied by many prey species
introduced from its native range. Machado Lake could be
considered primed for additional invasions by species from
the southeastern United States.
Given a lack of observed impacts to native species, the
isolated nature of the lake, and no quantified societal or
economic costs, Southern Watersnakes in Machado Lake
could perhaps be considered exotic, but not invasive. Such an
interpretation could be used to downplay the risks associated
with this population. This would be short-sighted, however,
because snakes in Machado Lake represent a source popu-
lation from which individuals could be intentionally trans-
ported (cf. Edwards et al. 2014) to areas that are more
ecologically sensitive. The habitat and dietary generalism,
and reproductive capacity, of N. fasciata imply high risks
of population establishment and impacts should individuals
be translocated to water bodies in California that do
contain imperiled native species. Major ecological restoration
of Machado Lake and the Wilmington Drain is currently
underway (City of Los Angeles 2014), and these activities
might be beneficial to Southern Watersnakes by increasing
prey abundances and providing opportunities for uninten-
tional transport of snakes to other water bodies via construc-
tion equipment or other pathways. Moreover, the lake is likely
to receive even more exotic species in the future; on three
occasions we observed brightly colored aquarium gravel in
shallow water along the shore, indicating spots where captive
aquatic organisms had been recently released. Our field
assistants also observed a group of monks releasing large
numbers (estimated in the thousands of individuals) of small
goldfish and koi as part of a religious ritual. For generalist
predators such as Southern Watersnakes, adding potential
prey species is likely to provide even greater opportunities
to attain high densities in the lake, thereby increasing
the likelihood of intentional or inadvertent transport to
other water bodies. Public education via informational
signs in multiple languages paired with outreach to specific
user groups could potentially reduce the rate of new
introductions.
Draining both Machado Lake and Wilmington Drain and
embarking on an intensive snake-control program would
provide the best chance of eradication, but such a course of
action would be opposed by park visitors, fishermen, and
birdwatchers. Traps, visual surveys, and/or other available
control tools might serve to suppress the population of an
undrained lake, but even a sustained high-intensity effort
might be insufficient to achieve complete eradication.
Biological control, reproductive inhibition, and similar
methods are unproven for operational control of snakes,
and would require long-term research investments to bring
them to initial stages of field testing (Reed and Rodda 2009).
Recent discoveries regarding the attractiveness of prey-
based chemical cues (parvalbumins) to Southern Water-
snakes (Smargiassi et al. 2012), and/or estradiol-driven
induction of female sex pheromone in male thamnophiine
snakes as an attractant for other males (Parker and Mason
2012), appear worthy of exploration in a control context.
As compared with many other semiaquatic snakes,
Southern Watersnakes tend to exhibit fairly high detection
probabilities using minnow traps as a sampling method
(Durso et al. 2011), suggesting that vigilant land managers
might be able to detect incipient populations elsewhere
outside the native range before high population densities are
achieved. Molecular tools such as environmental DNA
(Hunter et al. 2015) might provide a cost-effective tool for
detecting watersnake populations at low densities. If in-
cipient populations are detected, intensive rapid-response
efforts might allow local eradication.
Acknowledgments.—Funding for this study was awarded to the U.S.
Geological Survey (USGS) by the U.S. Fish and Wildlife Service under the
auspices of the Science Support Program, and was supplemented
by the Invasive Species Program of the USGS. We thank J.D. Willson,
S. Schuster, L. Bonewell, D. Attaway, K. Baumberger, B. Leatherman,
B. Trevett, C. Winne, J. Hakim, M. Fuller, E. Stitt, P. Balfour, R. Gallant,
J. Herod, A. Wells, and members of the Southwest Herpetological Society
for facilitating the project, providing information and/or assisting with
fieldwork. H. Strauss, J. Lan, and M. Byhower conducted the lion’s share of
fieldwork. Research and access permits were provided by the California
Department of Fish and Game (Permit 802046-02) and City of Los Angeles;
this study was approved by the Institutional Animal Care and Use
Committee of the USGS Fort Collins Science Center. Any use of trade,
product or firm names is for descriptive purposes only, and does not imply
endorsement by the U.S. Government.
0 Herpetologica 72(2), 2016
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Accepted on 16 December 2015
Associate Editor: Pilar Santidria´n Tomillo
REED ET AL.—ECOLOGY OF NONNATIVE NERODIA 0